Rubber reinforcing steel cord

Abstract

The steel cord has the 1x9 structure, in which three core wires and six thicker outer wires are twisted in the same direction with the same pitch, and has a flat shape in the section which is taken perpendicularly to the longitudinal section thereof. The six outer wires having at least two gaps between adjacent ones and the core wires have at least one gap between adjacent ones.

What is claimed is: 
     
       1. A steel cord for reinforcing a rubber article or the like, comprising nine wires twisted in a common direction and with a common pitch and composed of three wires forming a center core and six wires forming an outer jacket and having a larger diameter than that of said three center core wires, wherein the improvement resides: in that said steel cord has a flat shape in the section taken perpendicularly to the longitudinal direction thereof; in that said six outer wires surround said three core wires and have at least two gaps (S) between their adjacent ones; and in that said three core wires have at least one gap (s) between their adjacent ones, wherein said flat section has a longer diameter D 1  and a shorter diameter D 2  at a ratio of D 1  /D 2  of 1.05 to 1.20.   
     
     
       2. A steel cord according to claim 1, wherein the elongation is in the range of 0.090 to 0.125% when a load increasing from 0 to 5 Kg is applied thereto. 
     
     
       3. A steel cord according to claim 1 or 2, wherein said outer wires and said core wires have diameters no more than 0.5 mm, and wherein said outer wires have a diameter 1.5 to 2.0 times the diameter of said core wires. 
     
     
       4. A steel cord according to claim 3, wherein the twisting pitch is 10 to 20 mm. 
     
     
       5. A steel cord according to claim 3, wherein it is manufactured by preforming said core wires and said outer wires so as to have a diameter greater than that of a cord formed by tightly twisting said wires by twisting said nine wires into a coarse steel cord C' having an open structure, and by compressing said steel cord C' positively by means of a forming roll unit. 
     
     
       6. A steel cord according to claim 5, wherein it is manufactured by preforming said core wires and said outer wires so as to have a diameter greater than that of a cord formed by tightly twisting said wires by twisting said nine wires into a coarse steel cord C' having an open structure, and by compressing said steel cord C' positively by means of a forming roll unit. 
     
     
       7. A steel cord according to claim 1 or 2, wherein the twisting pitch is 10 to 20 mm. 
     
     
       8. A steel cord according to claim 1 or 2, wherein it is manufactured by preforming said core wires and said outer wires so as to have a diameter greater than that of a cord formed by tightly twisting said wires by twisting said nine wires into a coarse steel cord C' having an open structure, and by compressing said steel cord C' positively by means of a forming roll unit.